This invention relates to a method for producing a low acid beverage in which deterioration in quality associated with a pH decrease during heat sterilization or during long-term storage in a heated condition is minimized or eliminated.
Non-carbonated canned beverages can be generally classified into two types depending on the hydrogen ion concentration exponent (hereinafter referred to as xe2x80x9cpHxe2x80x9d) of the contents: acid beverages having a pH of less than 4.6, which include fruit drinks, sport drinks, tomato juice, and so on; and low acid beverages having a pH of 4.6 or above, which include black coffee, white coffee, milk tea, milk, green tea, soup, and so on (Beverage Japan No. 80, August 1988, xe2x80x9cProduction of Canned Beveragesxe2x80x9d). Under the Japanese Food Sanitation Law (Standards for the Foods and Additives, D, each Article), beverages that have a pH of 4.6 or above, and water activity in excess of 0.94 are required to be sterilized by a method such as is effective in destroying microorganisms introduced into beverages from raw material sources, etc. and which have the ability to survive and proliferate in such beverages. Low acid beverages generally require heat sterilization at 100xc2x0 C. or above.
However, heat sterilization causes a decrease in the pH of low acid beverages. Furthermore, long-term storage in a heated condition (55 to 60xc2x0 C.) such as is employed in vending machines also causes a decrease in pH. In addition, environmental factors may cause a rise in temperature of beverages during storage or distribution, thus similarly affecting the pH thereof.
Decreases in the pH of such beverages impart an undesirable acid taste and tend to impair flavor. Particularly, beverages containing milk, typified by canned white coffee, are subject to the problem that milk proteins tend to aggregate and precipitate, and milk fats tend to separate out if the pH of the beverages decreases to 6 or below (Journal of the Agricultural Chemical Society of Japan, A collection of summaries of lectures at the 1998 Congress, page 310, 3B7a4, Aoyama et al.).
As a means of solving the various problems associated with pH decreases as discussed above, one alternative is to increase pH buffering action. However, merely increasing the added amount of a pH regulator, such as sodium bicarbonate (sodium hydrogen carbonate) or disodium hydrogenphosphate, which has been employed as a means of regulating beverage pH levels or increasing buffering action, results in various undesirable effects as regards taste and texture. Specifically, a salty taste and sliminess tend to be imparted to the thus-treated beverage, and a thickening effect is evident in the texture. Thus, the original taste of a beverage will be impaired.
Japanese Unexamined Patent Publication No. 1997-37714 discloses a method for suppressing pH decreases, comprising incorporating a milk substitute component. However, this method comprises decreasing or eliminating lactose, a component which is considered to be responsible for acid formation, and the method does not in fact enhance pH buffering action. Moreover, the use of a milk substitute component is liable to change the flavor and taste of a beverage.
Japanese Unexamined Patent Publication No. 1997-9935 discloses a method by which various inorganic ion components, which are water-soluble forms of land plant ashes, exhibiting alkalinity, are added as pH regulators to beverages. However, this publication makes no concrete mention of a pH buffering action.
Therefore, the object of the present invention is to provide a low acid beverage which does not suffer from the problems of quality deterioration associated with pH decreases during heat sterilization or during long-term storage in a heated condition.